An MTJ (Magnetic Tunnel Junction) element is used as a magnetic memory element of an MRAM (Magnetic Random Access Memory). An MTJ element 10 contains magnetic materials and insulating materials, such as MgO. Therefore, the MTJ element 10 is hardly processed by RIE (Reactive Ion Etching) using a halogen gas that is usually used in a semiconductor device field. When the RIE is used to process the MTJ element 10, a corrosion problem caused by a low corrosion resistance is generated. Additionally, unfortunately the etching cannot originally be performed to the MTJ element 10 because the MTJ element 10 contains many hardly-etched materials.
Therefore, as measures of the problems, ion milling in which an Ar ion of an inert gas is used is studied to process the MTJ element 10. However, in the ion milling in which the Ar ion is used, because an atom is physically flicked, a leak current is passed through a tunnel barrier layer of the MTJ element 10 by re-adhesion of the spattered atom. Accordingly, in the ion milling of the MTJ element 10, dielectric breakdown becomes problematic due to a re-deposition layer 20, and the MTJ element 10 free from a short circuit is hardly processed.